While this article does have a good amount of relevant information, there are several places where references are needed to back up evidence, and as such, its not quite ready for GA status. Its not far off though, so I'm putting it on hold until these things can be fixed.
- Bluelinks need to be added to the 'Applications' section.
- More references need to be added for the more 'non-standard' knowledge, such as death potential in the lead paragraph, and most if not all of the Applications and History sections.
- 'Radon therapy' section is already mentioned in 'Applications'; this only needs to be mentioned once.
Here is my generic GA review of the article:
- It is well written.
- a (prose):
b (structure): c (MoS): d (jargon):
- a (prose):
- It is factually accurate and verifiable.
- a (references):
b (inline citations): c (reliable): d (OR): 
- a (references):
- It is broad in its coverage.
- a (major aspects): b (focused):
- a (major aspects):
- It follows the neutral point of view policy.
- a (fair representation): b (all significant views):
- a (fair representation):
- It is stable.
- It contains images, where possible, to illustrate the topic.
- a (tagged and captioned): b (lack of images does not in itself exclude GA): c (non-free images have fair use rationales):
- a (tagged and captioned):
- Failed due to lack of progress with problems stated above. Smomo 22:40, 5 March 2007 (UTC)